In a dynamic wavelength division multiplexing (“WDM”) network, unintended changes or “drift” to the wavelength of a transmitter component can result in severe signal degradation and network disruption. In order to avoid wavelength drift, transmitter components may be monitored for changes to operational characteristics including wavelength, output power, side-mode suppression ratio (SMSR) and relative intensity noise (RIN).
Existing systems for monitoring output signals from tunable lasers typically employ a complicated electronics circuit that monitors the output of a single resonator device to identify a shift in signal wavelength. Also, existing systems are typically formed from non-monolithic discrete components. FIG. 1 provides a diagram depicting an existing wavelength stabilization system or wavelength locker. As shown in FIG. 1, existing wavelength lockers comprise lens 110, beam splitter 112, etalon 114, and photodiodes 116, 118. Lens 110 collimates light emerging from a transmitter (not shown) before it is divided into two paths by beam splitter 112. One light path contains photodiode 116 which is used to monitor laser power. The second light path consists of etalon 114 and remaining photodiode 118 which are used to monitor laser signal wavelength. Etalon 114 has a periodic transmission characteristic designed to correspond to the WDM channel spacing. Variations in the signal intensity emerging from etalon 114 indicate a change in laser wavelength. An electronic feedback control loop (not shown) monitors the output from photodiode 118 and adjusts the transmitter parameters such as current, temperature, etc. so as to maintain the desired wavelength output.
In existing stabilization systems such as that depicted in FIG. 1 wherein a single wavelength monitoring device—etalon 114—is employed to identify a peak in the output signal, a complicated electronic feedback control loop is required to interpret the etalon output and determine what feedback steps should be taken to arrive at the desired wavelength.
Also, existing wavelength stabilization systems typically consist of separate and non-monolithic components. Such systems often have a relatively large form factor in order to accommodate the several discrete components. Production of wavelength stabilization systems from discrete components involves the additional complexity of aligning components on a submount and fixing the components in place. Indeed, existing stabilization systems are often subject to inaccuracies and instabilities resulting from imperfections in the alignment of discrete components. Moreover, the additional efforts directed at attempting to align components greatly increases the costs of manufacturing existing wavelength stabilizing devices.